81660385 has 16 divisors (see below), whose sum is σ = 105350400. Its totient is φ = 60569856.

The previous prime is 81660379. The next prime is 81660389. The reversal of 81660385 is 58306618.

It is a cyclic number.

It is not a de Polignac number, because 81660385 - 2³ = 81660377 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81660389) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4680 + ... + 13609.

It is an arithmetic number, because the mean of its divisors is an integer number (6584400).

Almost surely, 2^81660385 is an apocalyptic number.

It is an amenable number.

81660385 is a deficient number, since it is larger than the sum of its proper divisors (23690015).

81660385 is a wasteful number, since it uses less digits than its factorization.

81660385 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18360.

The product of its (nonzero) digits is 34560, while the sum is 37.

The square root of 81660385 is about 9036.6135803187. The cubic root of 81660385 is about 433.8475417835.

The spelling of 81660385 in words is "eighty-one million, six hundred sixty thousand, three hundred eighty-five".